This PDF file contains the front matter associated with SPIE Proceedings Volume 12066, including the Title Page, Copyright information, and Table of Contents

In order to improve the scale factor stability of interferometric fiber optic gyroscope (IFOG), laser is considered to be an alternative to traditional broadband light source because of its excellent frequency stability. Although the performance of IFOG driven directly by laser is inspiring, it is still necessary for further improvement. The main limiting factor is its narrow linewidth and errors of coherent backscattering, polarization coupling and Kerr effect will be reintroduced in laser-driven IFOG. At present, one of the best methods is using Gaussian white noise (GWN) to drive an external electro-optic phase modulator (EOM) and broaden the optical spectrum of laser which will not cause additional frequency drift to the laser. This review studies the mechanism of phase modulation comprehensively based on theory and simulation. The process of broadening is described by numerical calculation and OptiSystem platform. The spectrum is also broadened as expected in the experiment observed by optical spectrum analyzer (OSA). Furthermore, by broadening the linewidth before laser enters the IFOG system, its angular random walk noise and drift are improved by more than 60% compared with no modulation. The test results also show that the drift has reached the level of broadband light source. Related work enriches the application of laser as light source in IFOG and the research about external phase modulation.

We propose a fiber Bragg grating sensor interrogation system based on a Fourier domain mode-locked optoelectronic oscillator (FDML-OEO). The FDML is achieved by synchronizing the period of the driving current of the laser with the round-trip time of the OEO loop. By employing a narrow band electrical filter with the central frequency located within the sweeping frequency of the FDML-OEO, pulsed microwave output can be obtained. The wavelength shift of the phase-shift fiber Bragg grating (PS-FBG) can be interrogated by measuring the pulse interval variation. The experimental results indicate that the pulse interval of the generated signal has a linear relationship with the axial strain applied to the PS-FBG and a sensitivity as high as 0.42 μs/με is achieved.

In this paper, an analytical model of the nonlinear inter-core crosstalk (NICXT) for real weakly coupled MCFs is derived initially basing on the coupled-mode theory (CMT) with bending and twisting perturbations. Novel linear power-coupling coefficient (LPCC) and nonlinear power-coupling coefficient (NPCC) are derived for the modified coupled-power equations (CPEs) by using the split step Fourier method (SSFM) and perturbation method (PM). Numerical simulations are carried out based on various parameter configurations for the MCFs transmission system considered. Our researches indicate that the fiber nonlinearity will reduce the phase-matching points (PMPs) effectively under the condition of a high optical power. The theoretical simulation results agree well with the experimental results.

This paper reports the design of a double layer micromachined chiral metasurface. The cou-pling of the two layers can be tuned via shifting the unit cells of the top layer. The tunable metasurface has large optical activity in terahertz frequency range. Furthermore asymmetric transmission of 16% is also demonstrated in the numerical simulation. The rotation angle and asymmetry can be actively tuned through micromachined actuator.

We design and investigate a 10 Gb/s single user hybrid fiber-free space optical (FSO)-fiber experimental system based on optical code division multiple access (OCDMA). The receiving eye diagrams of legitimate user and eavesdropping user are measured, and the reliability and security of the hybrid system are analyzed through the eye diagrams. In order to analyze the security of the hybrid system, a tunable attenuator is used to simulate the eavesdropping situation of eavesdropping user at different position of fiber links. When analyzing the reliability of the system through the eye diagrams of legitimate user under different turbulence effects and different received power, we can see that the system can achieve reliable transmission with low-power reception only under weak turbulence. In the case of middle and strong turbulence, some measures must be taken to ensure the reliable transmission of the system. When analyzing the security of the system, the eye diagrams of eavesdropping user under the different turbulence effects and different eavesdropping distance are measured. It can be seen from the eye diagrams that the eye diagram in the second 20km optical fiber is worse, because Eve's eavesdropping signal in the second section of fiber is affected by the turbulence in FSO channel. The experimental results show that the hybrid fiber-FSO-fiber system based on OCDMA can achieve reliable transmission to ensure reliability, and also shows the good security through the poor eavesdropping.

The combination of phase change materials and metasurfaces has enabled myriads of versatile platforms for dynamic wave control, especially for various applications in integrated photonics and optoelectronics. In this paper, an electrically reconfigurable metasurface is demonstrated to work as a terahertz (THz) broadband digital switch by integration of vanadium dioxide (VO2). In such integrated optoelectronic frameworks, active and bistable digital control of optical responses is enabled by applying electrical stimuli to vertically cascaded metasurfaces with broadband behaviors for Joule heating that causes phase change and state switching. Before and after phase change, a high contrast ratio of transmittance is demonstrated within a broad THz range up to 400 GHz. Essentially, fast switching can be guaranteed compared with current devices based on thin film phase change materials, due to the local electrical heating that proves inherently efficient and faster to trigger the phase transition process. As a result, such active optoelectronic framework based on phase change materials may pave a new way for emerging integrated devices such as photoelectric switch, photonic memory, signal processing and so on

A novel optical fiber sensor based on weak coupling twin-core fiber (TCF) is proposed and experimentally demonstrated. The sensing structure consists of two single mode fibers (SMF) and fabricated by program controlled tapering the spliced region between the first SMF and a segment of TCF. During this period the light power was gradually transferred from the SMF into the cladding mode near the waist zone, after the waist zone, the optical power was gradually concentrated from the cladding mode into the cores mode, which could affect the extinction ratio of the interference peaks in the transmission spectrum. In order to obtain better interference spectrum, we adjusted the fusion structure of the tail fiber and the TCF, and the cross sections of the optical fibers are dislocated to a certain extent, so that the interference process of the beam changes. In the process of adjusting the structure, we observed the spectral changes in the spectrometer at the same time until the best interference spectrum appeared, and then we completed the fusion. The interference between different modes can be affected by changes in the external environment, like refractive index (RI) and strain, which also dictates the wavelength shift of the transmission spectrum. In the experiment, we have studied the sensing response of the optical fiber sensor to the RI and strain, and the sensing sensitivity is 131.1nm/RIU and 1.26x10^-3 dB/με respectively. All sensors fabricated in this paper show good linearity in terms of the spectral wavelength shift.

Because it is not possible to integrate the light source on the silicon-based photonic chips, it is necessary to study the efficient coupling method to coupling the light from the fiber into the chip. In order to ensure the high coupling efficiency, the edge coupling method is adopted in this paper. The simulation is carried out in the COMSOL software. The incident light is set as a Gaussian beam with a waist diameter of 2.5 μm and a wavelength of 1550 nm to simulate the light emitted from the lensed fiber. The incident region of the waveguide adopts an inverse-nanotaper design, that is along the direction of light propagation, the width and height of the waveguide in the taper region gradually increase and keep constants in the bus waveguide region. In this paper, the specific size of the designed inverse-nanotaper coupler is given, and the coupling efficiency of the edge couplers under different conditions is analyzed, which lays a certain foundation for on-chip integration of related devices.

For augmented reality applications, the micro display panels are generally used, as a straightforward method for display engines. But there are the light efficiency and vergence accommodation conflict problems, which affect the performance and application of the AR glasses, HMD and HUDs. One way to solve the problem is to use holography display instead of direct display, which exploit the diffraction light instead of reflection light of the liquid crystal panel. One of the big problems is the form factor of holographic systems which use SLM. Most of current SLMs are composed of a driver board with FPGA and a liquid crystal on silicon panel. The FPGA driver board is big and very power consuming, which makes it better for general SLM systems that cares more about changing the driving algorithm flexibly rather than make it a wearable gadget. A compact SLM system is designed specifically for AR applications, which replaced the normally used FPGA system with a driver IC and greatly reduce they whole system size and power consumption while realize the same function for holographic display. The driver IC could receive the RGB signal or MIPI signal and transform the standard picture signal to a high frame rate color sequential signal, also the gray scale could be tuned through on chip registers either beforehand or instantly, which makes it good for liquid crystals working in different wavelength. The driver board is 2*6 cm² with a type-C connector which could easily transmit image data from a laptop or a cellphone. This form factor is almost the same with monocular glasses. The power consumption of the driver IC is around 250mW for the driver IC comparing to the normally 5W power of FPGAs. Also, the frame rate could be from 60 to 120 Hz. A simple Fourier holography optical system is used to demonstrate the holographic display, with a lens tear apart from a smart glass on the market. The 3D holographic is displayed in the lens.

The non-invasive detection of blood glucose based on photoacoustic spectroscopy is a very popular method used to monitor the diabetes mellitus in recent years. The basic mechanism of photoacoustic spectroscopy is the effect of photo-induced ultrasonic. The detection accuracy of blood glucose can be improved due to the captured ultrasonic rather than the photons. The properties of ultrasonic transducer is one of the important influence factors on the detection accuracy of glucose. To study the effect of detection frequency for ultrasonic transducer on the glucose detection based on photoacoustic spectroscopy, a set of photoacoustic detection system was established. The optical parameters oscillator (OPO) pulsed laser pumped with 532nm was used as the excitation light source. Three kinds of ultrasonic transducers with different central echo frequencies (1MHz, 2.5MHz, and 30MHz) were respectively used to capture the photoacoustic signal of test blood phantoms with different concentrations of glucose. The time-resolved photoacoustic signal and peak-to-peak values of test blood phantoms were obtained. The results show that with the increase of glucose concentration, the photoacoustic amplitudes and peak-to-peak values of phantoms increase. Moreover, the time of photoacoustic signal shifts left with the increase of concentration. The prediction models based on linear fitting method were established for three kinds of ultrasonic transducers. Prediction results show that for the ultrasonic transducer with central frequency of 1MHz, the correction coefficient is 0.8681, the root-mean-square error (RMSE) of glucose concentration is about 13.3%. For the ultrasonic transducer with central frequency of 2.5MHz, the correction coefficient is 0.83127, the RMSE of glucose concentration is about 1.8149%. For the ultrasonic transducer with central frequency of 30MHz, the correction coefficient is 0.99598, the RMSE of glucose concentration is about 0.3808%. Therefore, the detection effect of the ultrasonic transducer with central frequency of 30MHz is best compared with the two others.

In this paper, we proposed a high-frequency angular vibration calibration system based on phase modulated laser interferometer technique, which can provide the real-time rotation angle measurement with vibration frequency of up to 1000Hz. The optical configuration, operation principle, and phase generation carrier demodulation (PGC) technique of this calibration system are presented. Both theoretical and experimental results demonstrate that our proposed angular vibration calibration system can realize an angle measurement with an amplitude of 0.3” at angular frequency of 1000Hz.

Compared with the traditional mechanical scanning system, the silicon-based optical waveguide phased array has the advantages of fast scanning speed, low power consumption, small insertion loss, small size, light weight, and high integration. Therefore, it is used in intelligent driving, celestial navigation, genetic diagnosis, etc. Also many advanced fields such as new optical communications have huge application prospects. In this paper, theoretical simulation, layout drawing and device preparation are carried out on the device design of the silicon waveguide phased array system. The main research contents are as follows. First, by designing a reasonable cross-sectional size of the waveguide, it is verified that the SOI-based silicon optical waveguide has a lower electromagnetic wave loss in the local optical field in the TE mode. Secondly, the input grating coupler and output grating antenna structure for spatial optical waveguide transmission are designed, and the propagation direction and intensity distribution of the optical field in the grating coupler are obtained, indicating that the coupling efficiency and output efficiency are both greater than 50%. Meanwhile through the structure design and optimization of the multi-mode interferometer of multi-element phased array beam splitting, the output intensity reaches 90%. Finally, the 8-element and 16-element array layouts were drawn, and the corresponding all-solid phased array micro-nano structure was fabricated, the size of which was consistent with the design, laying the foundation for the next step of performance verification.

In order to further improve the measurement precision of the star sensor and solve the problem on displacement field construction for on-orbit star sensor mounting bracket. In this paper, star sensor mounting bracket is simplified, and the theoretical formula on the displacement field of the star sensor mounting bracket is constructed based on beam bending theory, curvature recursive method and the least square method. Secondly, fiber Bragg grating sensors are embedded in the key nodes of the star sensor mounting bracket, and the strain of the star sensor mounting bracket is measured by the static test. Then, the displacement field of the star sensor mounting bracket is constructed based on the strain test data, and combined with the theoretical formula for the displacement field. Finally, comparing the measured data of displacement mete with the constructed displacement field values and static simulation results, the feasibility and accuracy of the method on constructing the displacement field of star sensor mounting bracket by using embedded fiber Bragg grating for strain monitoring is further verified.

Silicon-on-insulator (SOI) waveguide is a competitive and technological platform for photonic integrated circuits because of its compatibility with mature complementary metal oxide semiconductor (CMOS) process. Silicon nanowires enable ultra-sharp bending due to their high refractive index contrast between the core and cladding layer of the waveguide, consequently allowing for a small device size. Unfortunately, the high dielectric contrast makes SOI waveguides highly polarization dependent, leading to a lot limitations for more practical applications of the SOI based devices. On-chip polarizers are important components for design and development of many optical-fiber coherent communication and optic sensing systems, such as switches, integrated-optic gyroscopes and polarization independent receivers for coherent detection in which only a specific polarization state is allowed. In this letter, a compact and low-loss TE passed polarizer was proposed and designed and optimized based on surface plasmon polaritons SOI platform where a 220nm-thin silicon layer acts as the core layer on top of a 2-μm silica buried layer. The structure used for SPPs based polarizer consists of a dielectric waveguide and metal slab film with a low-index spacer layer separated. In such a structure, surface plasmon resonance is achieved by the evanescent wave from the light beam being totally internally reflected inside the high-index silicon core layer with phase matching conditions satisfied. The fundamental TM filed is coupled into the plasmon mode concentrated in the close vicinity of the metal/dielectric interface. In contrast, the fundamental TE mode is mainly guided in the silicon core region. As a result, the TM mode behaves a larger absorption loss due to the existence of the imaginary part in the metal permittivity, and the TE mode is slightly affected. For a proper design of the waveguide dimensions, the TM mode propagating through the polarizer will suffer significant attenuation while the TE mode keeps a low propagation loss, thus providing a high polarization extinction ratio. Effects of important design parameters, such as metal material, spacer thickness and refractive index, on the performance of the polarizer are compared and analyzed. FDTD simulation results show that, a 5 μm-long polarizer with SiN spacer and Cr cladding could provide a high polarization extinction ratio of more than 20 dB with an excess loss of TE mode less than 0.27dB at 1.55μm wavelength over a 140 nm broad bandwidth. And the insertion loss can be further reduced to less than 0.2 dB with a 10-μm polarizer length by increasing the buffer thickness. This compact and low-loss polarizer could be easily implemented with simple fabrication process.

Light-emitting diodes (LEDs) have been widely used in many fields. As a new packaging form, LED with chips scale package (CSP) has received more and more attention. The heat dissipation of LED devices is the main problem that restricts the application of LED, especially for 2835 Surface Mounted Devices（SMD）LEDs. In this paper, traditional packaging and CSP packaging methods have been used in 2835 SMD LEDs, and the changes of thermal resistance, spectrum, color temperature and color coordinates of the samples under different temperature and current have been studied. The thermal resistance results indicate that the 2835 SMD LEDs with CSP package has better temperature and current stability than that with traditional package. The 2835 SMD LEDs with CSP package have better spectral integrity at different current and temperature condition. The color temperature of the two samples almost changes linearly with increasing current or temperature. The result indicates that the blue light emission from the blue LED chip increases with current increase, which leads to shifting in the chromaticity coordinates to the blue portion in the chromaticity diagram that known as a blue shift mechanism for 2835 SMD LEDs with traditional package. On the contrary, the chromaticity coordinate X of 2835 SMD LEDs with CSP package have increased, which mainly attributed to the reduction of photon reabsorption. The long wavelength phosphor stimulated by more blue light as well as purple light with increasing intensity of current, so the color coordinates moved to the red region.

Optical holographic data storages (HDS) with the high theoretical-capacity density proportional to 1/λ3 have been researched for more than two decades. Among them, the coaxial HDS is current research hotspot. Amplitude-based coding in coaxial holographic storage systems is fundamental and generally employs a 3:16 encoding scheme that sets merely 3 non-adjacent bright pixels within a 4*4 pixels data block with the coding rate of 0.5. This data format is called three-level format (TLF). Unfortunately, the data frame recorded upon the disc is difficult to be recovered accurately in the practice due to the system inherent complexity such as light intensity and distribution, mechanical movement, dynamical focalizing, material distribution, servo subsystem, and component quality. This paper experimentally analyzes inaccurate TLF data frames recognition and its corresponding factors. We design an experimental approach to evaluate the quality of recorded data frames, and we also conclude several observations. First, the luminance among bright pixels within synchronization block consisting of 4×4 bright pixels are unevenly and distorted actually, making the synchronization block locating inaccurately. Second, the distance between two adjacent bright pixels heavily affects the recorded image quality. Third, the high aggregate brightness of a data frame severely reduces the frame’s signal-to-noise ratio. Forth, the recorded image suffers from the picture distortion, but the degree of distortion is slight within an acceptable range. Last, holographic material distribution upon disc also affects the brightness and pixel consistency. Based on these observations, we discuss several solutions to improve the reading accuracy for hologram data frames.

In this paper, we propose a novel routing, core, and spectrum assignment (RCSA) algorithm based on inter-core spectrum crosstalk measurement with dedicated path protection (RCSA-IC-SCM). We also introuduce two other RCSA algorithms with the no inter-core spectrum crosstalk measurement (RCSA-noIC-SCM) and traditional inter-core spectrum crosstalk measurement (RCSA-TIC-SCM) for comparison. Compared with other traditional RCSA algorithms, simulation results demonstrate that our proposed RCSA-IC-SCM algorithm achieves a better performance in terms of average inter-core crosstalk, blocking probability, and spectrum occupation ratio in spatial division multiplexing elastic optical networks (SDM-EONs).

Based on the development trend of silicon-based optoelectronic technology and industry, and combined with the development status of microelectronic integrated circuits with feature sizes reduced to a few nanometers, as well as tightly surrounding high-speed, high-density, low-power interconnection and computing for the research of optoelectronic integration technology, this paper summarizes the solution of photonic integrated circuit (PIC) and electronic integrated circuit (EIC) Co-package integration through optoelectronic co-package technology. The Co-packaged solution takes full advantage of the mature technology of microelectronics and the interconnection speed of photonic technology, large bandwidth, anti-interference, high density and low power consumption. The reliability of the solder joints of the ball grid array (BGA) in the photoelectric Co-package under the conditions of sinusoidal vibration and thermal shock was studied by using the finite element method(FEM). Studies have shown that vibration loads acting on multiphase structures can cause stress concentration at the sharp corners of the boundary between two different materials. Shear loading will cause stress concentration at the corners of Cu6Sn5 layer under thermal shock conditions. The mean time to failure (MTTF) was predicted by using FEM to be 2166h, which is consistent with the actual. A systematic description of the reliability of highly integrated silicon-optical switches.From the point of data center networking and switch port, the reliability of silicon-optical switches is analyzed, and a solution to backup the failed port of silicon-optical switches is proposed.

Phase-sensitive optical time-domain reflectometer (φ-OTDR) is widely used for safety monitoring of large-scale civil objects, by which external vibrations along the sensing fiber can be detected. It has to be noticed that the category of vibration signals should be accurately distinguished for many real applications. At present, an extensively approach of signal recognition is deep convolutional neural network (DCNN). In the work, the one-dimensional DCNN (1D-DCNN) is applied to recognize different sound-induced vibrations based on their time-domain intensity signals detected by an amplitude-demodulated φ-OTDR system. It is turned out that the DCNN successfully shows the capability of recognizing walking, rock drill, explosion, hand hammer, car siren, and background noises with a high accuracy. Additionally, the 1D time-domain intensity vectors are rearranged into 2D matrices and the 2D-DCNN is accordingly employed to identify these vibration signals. The confusion matrices demonstrate that the 1D-DCNN has a higher average recognition accuracy to identify the concerned sounds with respect to the 2D-DCNN.

We propose and demonstrate a 3dB optical power splitter based on silicon on insulator (SOI) platform. Simulations results show that 50:50 split ratio for TE₀ and TE₁ modes can be achieved simultaneously by mode dispersion engineering. A compact size of 28.1μm can be achieved by introducing subwavelength gratings (SWG) structure. The proposed device can be utilized for multi-mode signal processing.

With the rapid development of autonomous driving technology, the driving environment is becoming more and more complex, and higher requirements are put forward for car headlights. This paper proposes a smart headlamp with LED as the light source, Digital Mirror Device (DMD) as the core light distribution element, and free-form surface lens as the optical imaging element. The LED collimating outer lens is calculated by the theory of light refraction and reflection, and modeling and simulation are performed on it. Its optical efficiency meets the design requirements and achieves good light collection and collimation for the LED. According to the relevant specifications of the national standard and the structural characteristics of the DMD micromirror array. Using the principle of area segmentation to design standard patterns that meet national standards and DMD intelligent patterns in multiple traffic scenes; use theoretical calculations to obtain free-form surface imaging lenses. The processed LED light is modulated by DMD to form a specific intelligent pattern, and a free-form surface lens is used to achieve imaging and light distribution. The simulation analysis results show that the optical modulation performance of the system is good, and the optical efficiency meets the design requirements. A prototype of the intelligent light distribution system was built, and compared with the lighting effect after loading the standard pattern, its lighting index reached the national standard requirements, and the intelligent light distribution experiment under multiple intelligent scenes was completed. The system can flexibly load different lighting patterns to achieve clarity. Light projection.

A single sideband phase modulated radio over fiber link with improved spurious-free dynamic range is propsed, in which an optical processor is used for IMD3 suppression. A theoretical analysis is presented and the simulation experiment results indicate that the SFDR is up to 126.3 dB·Hz^4/5.

In this paper, we propose and demonstrate a mode insensitive micro-ring resonator which could process TE₀ and TE₁ modes simultaneously. The proposed device is composed of 90 ° modified Euler bend waveguide and deeply etched subwavelength grating (SWG) coupler. The curvature design of the Euler curve is smoother than that of the Bezier curve, thus reducing the size. The SWG waveguide can enhance the coupling effect by decreasing the refractive index difference between cladding and core compared to directional couplers and therefore it also reduces the size. Detail size of fabrication is performed, footprint is reduced by 46% to 170 μm. The proposed device could be utilized in advanced MDM transmission system.

In recent years, silicon photonics (SiPh) has generated considerable research interest and achieved rapid progress in coherent optical transceivers market. Automatic bias control (ABC) is an important technology of dual parallel Mach-Zehnder (MZ) optical modulators. Most researches have been investigated based on LiNO₃ modulator, but few on SiPh, in which many ABC algorithms become invalid due to the non-idealities. In this paper, a novel and effective ABC scheme for SiPh in-phase and quadrature (IQ) modulator is proposed, and investigated theoretically and experimentally. Compared to the convention method of LiNO₃, our algorithm is still robust in SiPh modulator with finite extinction ratios.

Diffractive optical elements (DOE) are widely used in modern optical systems due to their advantages of small size, light weight, high design freedom, wide material selectivity and unique dispersion performance[1]1. However, with the development of technology, the optical system has put forward higher requirements on larger diffraction angle, high diffraction efficiency and uniformity of DOEs. According to the grating equation, the diffraction angle can only be increased by reducing the feature size of DOE. When the feature size of the DOE is below the sub-wavelength level, the conventional scalar diffraction theory is no longer applicable. In this paper, an ultra-wide-angle 1×11 beam splitter is designed by using one-dimensional rigorous coupled-wave theory and genetic algorithm. The maximum diffraction angle of the beam splitter can be reach 72°and the diffraction efficiency is 92.98% with the uniformity error is 5.77%. By comparing with the FDTD simulation results, the difference in the diffraction efficiency of the DOE designed based on this method is less than 1%. This method has wide application prospects in the design of large angle beam splitters, structural light generation, holographic projection display and other fields.

High conductivity of non-polar a-plane p-type Mg-doped AlGaN epi-layers with Al composition up to 0.53 were grown by metal organic chemical vapor deposition (MOCVD). The p-AlGaN epi-layers with the Al composition varied from 0 to 0.53 were studied by various characterizations. In particular, the non-polar a-plane Mg-doped p-AlGaN epi-layers, using a novel MOCVD growth technique featured with pulsed mass flow supply (PMFS) of the metal organic-source, exhibited a high conductivity in the Al-rich p-AlGaN epi-layers. It was revealed that the electrical conductivity, surface morphology as well as crystalline quality were significantly enhanced due to the introduction of the newly-developed PMFS technique during the growth of the a-plane p-AlGaN epi-layers.

The wafer-level co-test of optical and analog chips is demonstrated to be cost-cutting solution for coherent optical device packaging. The extinction ratio test and the phase error test are illustrated for example.

In this paper, we report the influence of laser intensity on small dimensions of the microstructure for both exposure of graphic zone and blank zone. Also, the one-time electroplate technology and the two-time electroplate technology were conducted for production of optical discs. A series of laser intensities (30mW, 30%, 35%, 40%, 45%, 50%, 55%) are conducted through laser direct writing. The micropore size increased with the laser intensity for exposure of graphic zone to the laser which leaving holes on the surface of master disc, while the micropore size decreased with laser intensity for exposure of blank zone which leaving bosses on the surface master disc. Moreover, the optimum laser intensity is found to be 45% for both one-time electroplating and two-time electroplating. The micropore size remains the same size during the whole process indicating the excellent stability and reliability of the process. In addition, the demolding process during the production of optical disc is smooth due to the controlled angle between photoresist and nickel surface. However, the height of microstructure boss on the optical disc after injection molding depended on the size of the microstructure. The height of the boss was 150nm for 2μm zone while it was only 80nm for 1μm zone. This work proves the feasibility and potential use of a new physical format for long-life holographic storage disc, which may break monopolies in optical storage field, by applying one-time electroplating and two-time electroplating method.

With the wide application of micro-nano structures in various fields, micro-nano technology has been developed continuously. Among them, micro-nano surface morphology detection technology has become a research hotspot, because the surface geometry and morphology of micro-nano devices determine the functional level and service life of devices. With the increasing complexity of micro nano device surface morphology and the increasing sharp edges, the detection technologies are facing severe challenges. Among various detection methods, structured illumination microscopy (SIM) has attracted many research interests due to the characteristics of high accuracy, strong adaptability and high efficiency. The existing SIM are mainly based on phase-shift technique, Hilbert transform technique and global Fourier transform technique. However, for complex-surface and steep-edge measurements, it is difficult for traditional SIM to achieve both high accuracy and high efficiency. In this paper, a method based on SIM which combines vertical scan and phase-shift is proposed. In this proposed measurement system, vertical scanning of the object is synchronized with the switching of the phase-shifted fringe pattern and only one fringe pattern needs to be projected, which enables a point-to-point processing defined as local Fourier transform method in this paper to be utilized to extract the modulation information which will reserve high-frequency information of the image so it can be applied to both smooth and rough surfaces. Simulation and experiment are carried out to demonstrate that the proposed method can successfully realize fast and accurate detection of complex-surface and steep-edge.

We employ a Bayesian optimization (BO) approach coupled with electromagnetic solver to optimize the photonic nanojets (PNJs) respectively generated by a 2D cuboid and a 3D concentric cylinder. The operating wavelength is selected atλ = 632.8 nm. By optimizing a five-layer cuboid, we achieved a narrow PNJ with waist at the full width at half-maximum (FWHM) about w ~ 0.2λ and an ultra-long PNJ with a beam length 123λ , respectively. Whereas by optimizing 3D concentric cylinder, we achieved a narrow PNJ with waist at FWHM about w ~ 0.22λand ultra-long PNJ with a beam length 78λ , respectively. Furthermore, we explore the physics behind the PNJ phenomenon, such as the fundamentals of extreme PNJ generation and the relation between the objective intensity profile and the refractive index gradients across the structure. The proposed approach presents an alternative approach to the design of various photonic nanostructures and may provide conventionally-inaccessible physical insight to their functionalities.

Long-term stability of organic-inorganic metal halide perovskite solar cells (PSCs) is a prerequisite for their successful commercialization. Electrode failure is one of the most critical reasons for the degradation of perovskite solar cells during aging test. The electrode failure is dominantly due to corrosion of metal contacts by the iodine ion migrated from the perovskite active layer. To conquer the instability of PSCs, we inserted a compact ultra-thin Al₂O₃ interlayer between electron transfer layer and metal contact by atomic layer deposition (ALD) processed at 65℃. Experimental results show that 8 deposition cycle ALD Al₂O₃ thin film (~2 nm) improve the efficiency as well as the stability of the PSCs. It is found that the Al₂O₃ layer plays an important role of blocking iodide ion migration, preventing moisture and oxygen penetration and improving the efficiency of electron extraction. Statistically, the perovskite solar cells achieve a power conversion efficiency (PCE) of 19.50% (V_oc of 1.061 V, and J_sc of 23.03 mA/cm²), and remain 80% of its initial performance after 1200 hours of storage in ambient air condition, also remained 97.4％ of its initial performance when heated at 85℃ for 48 hours. Compared to the devices without ALD Al₂O₃ interlayer, the PCE is improved 12%, and the stability is extended for 400 hrs. This work highlights the importance of introducing ultra-thin compact ion blocking layer to the high performance perovskite solar cell devices.

Reflection and refraction images are treated as the texture of the object in computer graphics, which brings wrong depth information when focusing on the object in holographic display. In this paper, a method of ray tracing rendering with complete depth information for computer-generated hologram(CGH) is proposed. Correct depths of reflection and refraction images are calculated, and layer-based method is used to generate CGH. In experiment result, our method truthfully reconstructs the complete depth information of complex scene. Reflection or refraction images and its corresponding media surfaces can be focused on correct depth. All layer data is computed in a single ray tracing procedure, and the generation speed of 1024×1024 CGH for 3D scene divided into 10 layers is 100fps.

A large viewing angle 3D light-field display based on a single lens array with the optical-digital joint optimization algorithm is proposed. Aberrations generated by the single lens array are suppressed with the presented algorithm to increase the viewing angle. The proposed algorithm consists of aberration optional-correction module and digital image optimization module. Some aberrations selected by aberration analyses are suppressed to zero or minimums with the single lens unit optical structure in aberration optional-correction module, and residual aberrations are suppressed by pre-correcting based on Wiener filtering in digital image optimization module. Experimental results confirm that the optical-digital joint optimization algorithm can suppress aberrations effectively, and a 52-degree viewing angle 3D light-field display is realized.

Optical interferometry technology is one of the most accurate and effective detection methods. For the refractive index distribution measurement of G-Lens, we propose a method to calculate the order of circular interference fringes produced by a Mach-Zehnder interference optical system. This method is not only limited to the refractive index measurement, but also suitable for applications which is measured via interference method. For example, the surface error measurement of optical components. Several specific works had been performed such as effective area masking, image preprocessing, fringe center relocation, central-radiation fringe fractional-level calculation and fitting of circular optical interference fringe images. Furthermore, the two-dimensional distribution of cross-sections and three-dimensional of fringe orders are also obtained. In addition, we propose a new primary and secondary location method for the gray value peaks and valleys of noisy interference fringes, and on the basis of this location, the relative gray fringe fractional-level calculation is performed, which effectively avoids uneven illumination, noise, and the influence of unfavorable factors such as poor circularity and over-density of large-order fringes on the fringe calculation. For the work content of G-Lens refractive index distribution measurement, the algorithm has good repeatability accuracy, and the specific value is about 0.3‰.

As a typical miniaturized smart device, the miniature projection system is an important part of a head-mounted display device. In the micro-projection system with a LCOS or a DMD as the display chip, the performance of the lighting system directly affects the final imaging quality. We design and simulate two lighting systems based on compound eyes and a diffuser respectively. The design shows that without considering the loss of polarized light the light energy utilization rate of the system based on compound eyes is 70.3% while that of the system based on a diffuser is 25%, and with the ANSI nine-point sampling method the calculated uniformity of the system based on compound eyes is 91%, while that of the system based on a diffuser is 88%, and the axial length of the lighting system based on the diffuser is 0.6 times that of the lighting system based on compound eyes. According to the analysis of design results, the compound eyes based system results in higher energy utilization and uniformity compared with a diffuser based one. Since the compound eyes based system needs a relay system, it nevertheless has a larger volume. Therefore, it is necessary to choose a suitable lighting method according to actual needs of a specific head-mounted display device.

In recent years, the emerging global navigation satellite system reflectometry (GNSS-R) technology has become a research hotspot for its lightweight, high sensitivity and rich technology application scenarios. It has broad application prospects in the field of remote sensing detection and navigation technology. The role of GNSS-R remote sensing satellite in the field of marine remote sensing is becoming increasingly prominent. The acquisition of data and information and the observation performance of GNSS-R remote sensing satellite are not only constrained by the remote sensing equipment itself, but also affected by the satellite orbit. Based on the technical characteristics of GNSS-R remote sensing satellite, this paper proposes a grid based coverage efficiency statistical method, analyzes some influencing factors of GNSS-R remote sensing satellite efficiency based on the remote sensing task, and analyzes the influence of each factor on GNSS-R remote sensing satellite efficiency by modeling -It can provide theoretical reference for GNSS-R satellite orbit selection and optimization, onboard load design optimization and large-scale system construction.

The human visual attention mechanism promotes human to acquire the most important cues from large amount of information. However, most methods of simulating human visual attention now focus on 2D display, people know little about how human assign their visual attention under a 3D display. This paper firstly produced a saliency dataset consisting of human eye-fixation data for different 3D scenes under human quick glance, which demonstrated the human visual attention distribution. By analyzing the dataset, an approach based on convolutional neural network for human visual attention prediction under 3D light field display was proposed. The network is composed of three parts which are two-way feature extraction, feature fusion and prediction output. Comparing with saliency prediction models under 2D display devices, our proposed model can predict the distribution of human visual attention under 3D light field more accurately. This research promote further investigation of 3D applications such as 3D device evaluation and 3D content production.

3D light field display (LFD) which can reconstruct the emitted light field of objects in real world, provides human with natural 3D visual experience in the way of humans observing the real world without any glasses, and has attracted more and more attentions in recent years. However, most of the researches on 3D LFD focus on the improvement of display performance, and there are few researches on the performance evaluation of 3D LFD. In this paper, a 3D LFD performance evaluation method is proposed based on the performance measurement of air traffic control (ATC) task. ATC task is a comprehensive visual cognitive task, in which controllers need to obtain a lot of visual information to identify the aircraft collision situation in the dynamic scene as quickly as possible. The experimental independent variables were display conditions, including 2D display and 3D LFD with a viewing angle of 85 degrees. The number of misjudgments as well as the time taken to complete the task for different groups were counted. In order to decrease the influence of individual differences and learning effects on the 2D/3D experimental results, 15 subjects are tested in random order. The time interval between the two experiments was 5-7 days of each person. The superiority of the 3D LFD is demonstrated quantitatively by comparing results under different experimental conditions and using a statistical analysis method called the T-test.

Photonic-bandgap fiber (PBF) can effectively solve the problems of back-scattering and Kerr effect in the resonator for the resonant fiber optic gyroscope (RFOG). However, the polarization noise of PBF caused by temperature change still exists, needs to be tested and compensated. In our work, the mode transmission of a polarization maintaining PBF is analyzed. The birefringence and the temperature dependent birefringence of PBF are measured. The test results of the temperature dependent birefringence are basically consistent with the simulation in the environment above 0 °C, only one third of the traditional panda polarization maintaining fiber.

Matting is a method to extract foreground objects of arbitrary shape from an image. In the field of 3D display, matting technology is of great significance. Through the study of this technology, we can extract high-quality target foreground, and then reduce unnecessary stereo matching calculation and improve the effect of 3D display. This paper primarily studies the human target in 3D light field, and proposes a real-time multi-view background matting algorithm based on deep learning. Three-dimensional video live broadcast puts forward high requirements for the real-time performance of the matting algorithm. We pre-compose a group of multi-view images taken at the same time into a multi-view combined image. The network directly carries on the background matting to the multi-view combined image and outputs a group of foreground images at one time. Because the background of the multi-view combined image is not holistic, a pre-photographed background picture without human is added to the input to assist the network for learning. In addition, we add a channel subtraction module to help the network better understand the role of the original image and background image in the matting task. The method in this paper is tested on our multi-view data set. For pictures with different background complexity, it can run about 65 frames per second and maintain a relatively stable accuracy. The method can efficiently generate multi-view matting results and meet the requirements of 3D video live broadcast.

In this paper, we design a near-infrared 3D multifunctional metamaterial (3MM) to achieve several different functions based on modified direct binary search (DBS) algorithm. In order to demonstrate the versatility of 3MM, an optical absorber is obtained based on the inverse design technology. Besides, we also utilize it to achieve plasmon induced transparency (PIT) like effect. Finally, to prove the advantages of 3MM, we have designed the corresponding 2D metamaterial to realize the same functions based on the DBS algorithm for comparison. The comparison results show that the performance of 3MM is much better than the 2D metamaterial. Compared with previous works, our proposed 3MM not only demonstrates the advantages of 3D metamaterials in manipulating the absorption spectrums and PIT-like effects but also provides a general framework for other spectrum-related functions in various field, such as imaging, sensor, chemical analysis and so on.

A super multi-view display (SMV) technology is one kind of a promising method to realize the light field display approximately. It generates a dense viewing points with an interval smaller than the pupil diameter so that two or more rays passing through one object point in a three-dimensional (3D) space enter the pupil simultaneously. Therefore, a viewer could be able to focus on that object point. To produce a light field display with high 3D resolution while maintaining two or three rays entering the pupil, a flat panel system with high resolution or multiple display devices are required. To solve this problem, an SMV system with the slanted lenticular lens attached to a liquid crystal display (LCD) was developed in this article. The viewing zone is generated only around the viewer's eyes. Therefore, the resolution is improved by the reduction of the viewing zone. However, the viewing freedom is limited not only in the horizontal and vertical direction but also in the longitudinal direction. To increase the viewing freedom, an eye-tracking system is applied to the developed SMV system. The dynamical viewing zone characterizations including viewing interval, spatial distribution, and et. cl in this system was analyzed. To keep the viewer’s eyes always in the viewing zone with the smaller crosstalk, the compensation factors were calculated to generate the viewing zone depending on the 3D positions of the viewer’s eyes. The results show that the proposed SMV system successfully increased the horizontal, vertical, and longitudinal viewing freedom.

With the technological development of stereoscopic display, an immersive 3D space with large size can be reconstructed more and more easily, and a 3D spatial interaction method with high-efficiency become more and more urgent. Gesture interaction, as the most natural and efficient way of human-computer interaction, can convey information very quickly and efficiently. However, the effective interaction distance of most existing gesture interaction methods is less than one meter, and can not meet the demand of the long distance 3D spatial interaction. In this paper, an efficient network named Gesture YOLO for long-distance gesture detection is proposed to achieve the small gesture object detection with improved accuracy. There are two modules in our Gesture YOLO, one is the Dual CSPDarknet53-tiny Backbone module for fusing person features and gesture features, and the other is the Progressive Multi-Scale Feature Fusion module for enhancing output features. The experimental results on our test set show that our Gesture YOLO can achieve higher gesture detection accuracy than the YOLOv4-tiny at distances ranging from 2m to 5m, and can mitigate the significant drop in gesture detection accuracy when the distance increases.

Volume holographic storage with high storage density and access rate has excellent potential for large-scale data storage. However, data reliability is facing challenges and has become a main concern from various noise interference. In holographic storage systems with phase modulated, high raw bit error rates (RBER) are induced by optical noise, electrical noise, intra and inter page interference, reducing data reliability. In this paper, we exploits low-density parity-check (LDPC) coding with remarkable error correction capability to improve data reliability and capacity with minimizing read latency for phase modulated holographic storage. LDPC coding has a stronger error correction capability by adopting soft decision decoding with log-likelihood ratio (LLR) information. As a result, the bit error rates (BER) can be reduced and data reliability is significantly enhanced. In the process of the evaluation, we first count the variation of RBER with phase modulated under different single-to-noise ratio (SNR). Then, after using LDPC coding, we compare the sharpness of the modulated two-dimensional data pages to validate the effectiveness of utilizing LDPC coding. Moreover, we study the internal relationship between phase reconstruction with iterative Fourier transform algorithms and LDPC coding. The decoding iteration times and the number of Fourier iterations are counted. Simulation results show that LDPC coding can improve data reliability by decreasing BER.

Under the environment of MATLAB, a closed-loop feedback laser tracking system was established based on the dynamic prediction with Kalman filter and some other filtering processes. Different motion states of the tracked target are simulated to test the tracking performance. The following conclusions are obtained through simulations. After adding the dynamic prediction with Kalman filter, the tracking hysteresis can effectively be avoided when tracking the dynamic object. Taking advantage of the high frequency of PSD, the coordinate value can be read for several times in a feedback loop and then filtered to obtain a more accurate spot coordinate. Under static condition, the instability due to noise can be reduced through segmenting the feedback coefficient by distinguishing between the dynamic and static state of the object. According to the above designs, the results of the laser tracking system simulations show that the dynamic tracking performance is better than 100°/s, and static stability has an order of magnitude improvement than before.

Gabor zone plate (GZP) is typical amplitude-type diffractive lenses for high-resolution imaging. Compared with Fresnel zone plates (FZP), GZP can suppress all higher-order foci and shows better focusing performance. However, the focusing efficiency of GZP is very low and the cosine variation of its transmittance is difficult to satisfy. In order to improve these disadvantages, many kinds of improved Gabor zone plates are designed. However, the focusing efficiency of these Gabor zone plates are ~10%, which is still too low. A phase-type diffractive lens based on the Gabor zone plate is designed to improve the focusing efficiency of GZP, in which the radial distribution of microstructure varies in a cosine pattern. Simulation results show that the focusing efficiency of the Gabor-type diffractive lens (GDL) can reach ~22%, which is much higher than that of GZP. In addition, we also analyze the effect of errors of laser direct writing on the focusing efficiency of GDL and Fresnel-type diffractive lens (FDL). The results show that the focusing efficiency of GDL shows higher tolerance for the error of laser direct writing than that of FDL.

We present a 400G chip level Integrated Coherent Receiver optical-electronic testing system. The testing system shows high repeatability and high accuracy compared with commercial device testing system. Besides, we also achieve Graphical User Interface automated testing based on the system, which is high-efficiency for screening qualified chips or devices.

It is found that enhancing the coupling between the input or output tapers can cancel the intrinsic imbalance of a 2×2 multimode interferometer (MMI). Furthermore, a highly balanced 2×2 MMI is demonstrated with imbalance less than 0.1 dB in the full C-band by introducing a design with tilted tapers.

Traditional endoscopes use fiber bundles to transverse the images and have the disadvantages of large size and poor flexibility. Unlike the single mode fibers just guide the fundamental mode, multi-mode fibers (MMFs) accommodate a large number of guided modes. Accordingly, one MMF can be utilized to transverse imaging for endoscopy. This MMF based endoscope can effectively overcome the above shortcomings. However, there are effects such as modal dispersion and mode coupling in the transmission process of multimode fiber, which will cause the image transmitted in the fiber to be distorted or even unrecognizable. The randomness of fiber shape in fabrication detoriosate the distortion. By measuring the transmission matrix, it is possible to recover the image through MMF. But the overall shape and structure of MMF will change in the operation of endoscope. The transmission characteristics of multimode fiber are only closely related to the fiber geometry, but traditional MMF imaging techniques are applicable when the shape of the optical fiber during imaging is consistent with the shape of the optical fiber when the transmission characteristics are calibrated. This work will focus on solving these problems. This paper explores the imaging technology of single multimode optical fiber, proposes the use of neural network to fit the multimode optical fiber transmission matrix, and calculates the input light field through the reverse transmission matrix and the output speckle light field. The traditional real number network has limited fitting effect on the multimode fiber transmission matrix. Inspired by the physical process of multimode fiber modulation of the light field, the real number network is extended to the field of complex numbers, and complex number operations are implemented in the network in the form of real numbers. This article studies the imaging regularity and effectiveness of multimode fiber under the condition of slight deformation and severe deformation. The neural network fitting method of multi-mode optical fiber transmission matrix used in this paper can maintain its effectiveness within a certain deformation range, and has great application potential in some endoscopic applications.

With large storage capacity, low cost and long storage life, optical holographic storage technology has great application potential to meet the demands of quick data exchange and cold data storage. Accurate and standardized testing procedure of disc storage life about new optical storage media materials has become an important challenge. In view of the new optical storage technology, we discuss and analyze the applicability and limitations of the application of holographic optical disk life test through the existing domestic and foreign disc test standards. Because of materials changing in the holographic disc, we propose and optimize an aging test model and test procedure based on several discs aging test models. And also hope to provide a reference for the establishment of life test standards for holographic optical storage discs.

In recent years, graphene has been considered as the "king of new materials" be-cause of its special structure and excellent physical and chemical properties. It has been widely used in electronics, energy, materials, medical treatment and other fields. In this work, we propose a controllable method for the fabrication of gra-phene layers and devices by plasma etching of graphene films. Raman spectroscopy was used to investigate the effects of conditions such as gas ion selection, plasma power and plasma gas velocity on the number of layers and property of graphene. We found that this etching method introduces defects as it makes graphene thin, ar-gon etches faster than oxygen, and the increase in plasma power and gas velocity accelerates the etching process. So, choosing proper parameters is helpful to control the speed of etching process. In addition, we fabricated field effect transistor devices with variable and controllable performance and in-plane PN junction devices by using this method, and tested the change of photoelectric performance during the etching process.PN junction can separate the photogenerated electron-hole pairs and improve the re-sponsivity of light detection. Compared with the vertical structured heterojunction, the in-plane PN junction has higher mobility and higher current density. Due to the high precision of the e-beam lithography, complex structure functional devices based on several PN junctions combination can be fabricated. The external quantum Efficiency and specific detectivity of the PN junction devices by this method are higher. The method proposed in this work is relatively simple to implement and is expected to promote the development of related applications based on graphene films.

Orthogonal frequency division multiplexing (OFDM) has been applied to optical wireless communication to achieve high data rates and wide bandwidth and solve the issues of inter-symbol interference (ISI). Due to the non-negative and real-valued characteristics of intensity modulation/direct detection (IM/DD) signaling for optical wireless communication systems, some optical OFDM schemes have been proposed to reach the requirements. Among these optical OFDM schemes, adaptively biased OFDM (ABO-OFDM) reserves 1/4 of the subcarriers and utilizes Hermitian symmetry to generate non-negative and real values after invert fast Fourier transformation (IFFT) and adding bias in time domain. In this paper, we extend the original ABO-OFDM scheme and proposed a generalized ABO-OFDM scheme in which 1/m subcarriers are reserved for any positive integer m. It is demonstrated that the bias added in time domain can be counteracted exactly in frequency domain, which means it has lower implementation complexity at the receiver than most of the other optical OFDM schemes. This generalized ABO-OFDM scheme has higher frequency efficiency and lower peak-to-average power ratio (PAPR) than asymmetrically clipped optical OFDM (ACO-OFDM) and higher power efficiency than direct current biased optical OFDM (DCO-OFDM). We also evaluate the impact of parameter m on system performance in terms of PAPR and bit error rate (BER). Consider the comparison with other optical OFDM schemes and the tradeoff above-mentioned, the generalized ABO-OFDM is a potential scheme to facilitate optical wireless communications with a flexible parameter m.

In this paper, a 4×4 fixed-scale multi-input multi-output (MIMO) underwater optical wireless communication (UOWC) system is implemented with spatial multiplexing to achieve 20 Mbps rate over 2-m link distance which consists of 1-m free space and a 1-m water-filled tank. Experimental results suggested that the fixed-scale MIMO UOWC system shows more robustness than the conventional counterpart against our experimental setup.

Light field display is a true three-dimensional (3D) display technology that can produce full depth cues without using any special glasses. A super multi-view display (SMV) technology is one kind of a promising method to realize the light field display, in which a large number of views with an interval smaller than the pupil diameter was produced so that two or more rays passing through one object point in a 3D space enter the pupil simultaneously. Therefore, a viewer could be able to focus on that object point. However, the main bottleneck of its commercialization is the low 3D image resolution with a small field of view, shallow depth, and et. cl. which are limited by the bandwidth of the display devices. To solve this problem, an SMV system with the slanted lenticular lens array attached to a flat panel display was developed in this article. To produce a light field display with a high resolution while maintaining two or three rays entering the pupil, an eye-tracking system is applied. The viewing zone is generated only around the viewer's eyes. The resolution is improved by the reduction of the viewing zone. The crosstalk caused by the manufacture is another issue that affects the 3D image quality. The optical model is developed to simulate the optical characteristics of light field display based on the raytracing considering the fabrication error. The calibration method is proposed to compensate for the error and improve the image quality further.

Holographic displays enable the formation of a three-dimensional particle field distribution and is promised to be one solution of the key problems in present virtual and augmented reality displays. The biggest challenge in the computer-generated holography (CGH) is the high consuming calculation time and the restricted field of view due to the micro display screen. In order to solve the above mentioned problems, we propose a method for machine learning accelerated lensless holographic projection, which is based on the reconstruction of complex amplitude image from phase-only CGH. The runtime of generating the phase-only CGH is half of traditional iterative method. The complex amplitude image can achieve the maximum diffraction bandwidth of the spatial light modulator (SLM). The feasibility of this method is verified by experiments.

As an important diffractive optical element, the holographic grating has always been favored by users for its high diffraction efficiency and low cost. Especially in recent years, its value in the near-eye display waveguide structure has been further improved and explored. This paper derives a set of interference field theoretical models suitable for flexible curved radius grating, through the modification of the traditional two-wave interference principle. Based on this, the morphological law of the required interference pattern can be simulated. On the other hand, when we change the radius of flexible grating, the focus position of the diffraction field can be changed correspondingly, so as to achieve the purpose of quantitative focusing. Experiments show that the different degrees of bending of flexible curved radius grating can effectively adjust the focal length of the holographic element, and its diffraction efficiency can always be maintained above 88%. What’s more, the imaged brightness uniformity consistent, no interference of diffraction ghost lines, pave the way for the subsequent research on the key technologies of different surface-shaped curved waveguides.

Conventional metal-dielectric stacked hyperlenses based on hyperbolic metamaterials can reconstruct subwavelength information to the far field without loss, which is an effective method to break the Abbe diffraction limit. However, the radial resolution of most of current hyperlens is not high enough, which maybe hinders their applications in 3D precision imaging. Meanwhile, the presence of strong side lobes in the hyperlens far-field imaging is another issue, which not only weakens the main lobe, but also results in the overlapping of image points of multiple objects and the consequent difficulty in distinguishment. Here we propose a simple and effective method of achieving an incredible radial super-resolution imaging capability while having an outstanding side lobes suppression ratio (SLSR). Our structure for tubular hyperlens consists of alternating 92 pairs of Ag/Yi₂O₃ layers whose inner radius is 400 nm and the thickness of both Ag and Yi₂O₃ is 10nm. Then, we simply introduce the nano-gap layer into hyperlens by replacing Ag and Yi2O3 layers, and guarantee that the nano-gap layer is surrounded by Yi₂O₃ layers and the overall thickness of the hyperlens is unchanged. Corresponding finite element simulation results reveal that the radial resolution reaches the highest accuracy of 3 nm and SLSR achieves more than 3 dB at 365 nm TM-polarized source, which improves the imaging clarity extremely. The hyperlens we designed is of great significance for ultra-precision 3D optical imaging and real-time biomedical imaging. In addition, the application prospect on high performance sensing can be expected due to the super-resolution characteristics.

Diffusive photopolymer is one of the fastest developed fields on the application of the holographic optical storage, and has the advantages of huge data capacity and low coat. Based on the extended model of the nonlocal polymerization-driven diffusion, the photophysical mechanism of the dual monomer system in the photopolymer holographic material is introduced. The diffusion coefficient, polymerization rate and diffusion rate are determined experimentally to provide the conditional parameters in the model. Quantitative analysis of photopolymer formulation, refractive index modulation and diffraction efficiency. This analysis can improve material performance and provide a basis for the development of next-generation holographic storage materials. A nonlocal diffusion model is used to predict theoretically the grating evolution. The model has been developed to account for both nonlocal spatial and temporal effects in the medium, which can be attributed to polymer chain growth and corresponding polymeric kinetics equations are given. We find the relationship between these equations and refractive index modulation, and obtain a diffraction efficiency equation which is appropriate for transmission volume grating. The proportion of dual monomer in chemical reaction system was optimized, and the high optical transparency of photopolymer film were obtained.

Underwater wireless optical communication (UWOC) highly depends on the alignment between the receiver and transmitter in realization. In practice, the facts that laser sources have narrow divergence angles, water body suffers from fluctuation, and precise positioning is very difficult in the underwater environment bring great challenges to the link alignment as well as practical implementation. However, due to the intrinsic optical properties of seawater, photons will be scattered during the transmission process, resulting in the diffusion of light, which relaxes the requirements for strict alignment. Inspired by the uniform spatial distribution of the multi-source arrays with a close spacing, in this paper, we investigate the bit error rate (BER) performance of the multi-input single-output (MISO) laser links in the presence of receiver offset. Based on a system model by considering scattering and absorption effects and noises including background noise and blackbody radiation as well as OOK signaling and an ideal photon counter, we derived a closed-form expression of relationship among BER, transmit power, link range, receiver aperture and offset distance, which is verified by Monte Carlo simulations. Numerical results suggest that, regardless of water types, linear light source arrays parallel to the offset direction can improve the tolerance of receiver offset with specific transmit power and link range for reliable communications. On this basis, we compared the anti-offset performance in the case of different inter-spacings of light source arrays such as dual-source and three-source schemes and also derived the optimal inter-spacing for light source to maximize the acceptable offset distance with reliable communication for dual-source links.

Underwater wireless optical communication (UWOC) has been regarded as one of the promising solutions to underwater wireless communication systems due to its advantages of high bandwidth, fast transmission and good confidentiality. In UWOC systems, after emitting from light source, photons will be scattered with random deviated angles before propagating to the receiver plane. Hence, the light beam suffers a spatial angle spread at the receiver side. In order to improve the system performance with an appropriate receiver design, it is of significance to figure out the angle of arrival (AOA) distribution of the received light beam. In addition, the UWOC channel is susceptible to other effects such as absorption, turbulence and bubbles, especially when it is exposed to the complex ocean environment. Therefore, analyzing the impacts of these factors on AOA distribution is also essential to evaluate UWOC system performance. The existing studies of AOA distribution only considered single scattering component, which is not practical for turbid water. Furthermore, there are few studies focusing on multi-source scenarios. In this paper, we first present a simple expression for AOA distribution with single light source, taking both single and multiple scattering components into account. Then we extend the work to multi-source scenarios and derive the corresponding closed-form expression of AOA distribution. Compared to the traditional single scattering case, numerical results show that the proposed AOA distribution can fit well with Monte Carlo simulation results with various water types, link distances, and the characteristics of actual light sources.

Vanadium dioxide (VO₂), a thermochromic material with a low phase transition temperature at 68℃ and the magical hysteresis property near the phase transition temperature, has been widely investigated because of its potential application as infrared detector, optical switch, memristor, and ‘smart window’. Graphene, due to its special electrical, optical and thermal properties, has been extensively studied in recent years with layered hybrid structures of other materials. In this paper, to realize flexible manipulation of VO₂ phase transition, we co-designed a graphene heater to locally modulate temperature of VO₂. Typical thermal induced phase transition by temperature control stage has been achieved through electrical measurements, which shows the resistance of VO₂ has gone through a dramatical change over 3 order of magnitude around the critical temperature (68℃). As for the in situ heating manipulation, we applied current to the graphene to generate joule heating, which would result in a hot-spot to locally modulate the temperature of VO₂ to reach the phase transition point. Meanwhile, the electrical current of graphene that results in the structural phase transition of VO₂ could be smaller by inserting Al₂O₃ capping layer between graphene and VO₂. Compared with the traditional macroscale VO₂ device, our nanosized co-designed structure shows both low power consumption and fast response, which would benefit a lot in exploring VO₂ based on-chip electronic applications. In addition, we believe that the designed composite structure has a wide range of research significance in optoelectronic devices.